Reliable in-vivo penetration and transdermal injection using ultra-sharp hollow microneedles

Minimally invasive microneedles is a promising technology for painless drug administration through the human skin. However, not all microneedle structures are capable of penetrating the human skin in a repeatable and reliable fashion at moderate insertion forces. In this work we present an ultra-sharp hollow microneedle array, tailored for enhanced and reliable skin penetration capability. The microneedle apex has a tip radius below 100 nm. We show penetration and sustainable injection of liquid dye into dry living human skin without the use of any penetration enhancers. Microneedle liquid injection was also tested on clinically relevant sites, such as the shoulder and the upper arm. The electrical impedance was measured between the microneedle and a counter electrode showing continuous changes in the measured values during the insertion.